Food Protein Induced Allergic Proctocolitis

Food protein induced allergic proctocolitis is a non-IgE-mediated food protein allergy causing inflammation of the distal colon and rectum in the first months of life, presenting with blood streaked, mucous stools in an otherwise healthy, thriving infant.

• Onset typically between 2 and 8 weeks of age (range days to 6 months); about 60 percent in exclusively breastfed infants (maternal dietary proteins pass in breast milk), the remainder in formula fed infants (cow's milk or soy).
• Common triggers: cow's milk protein (commonest), soy, egg, corn, wheat.
• Mechanism: T-cell mediated eosinophilic infiltration of the colonic mucosa; self-limited.
• Prevalence about 0.16 to 17 percent of infants in different series (up to 18 percent of breastfed infants with rectal bleeding).
• Natural history: tolerance develops by 9 to 12 months in most (more than 90 percent by age 1 to 3 years).
• Differentiation: FPIES (profuse vomiting, shock), eosinophilic gastroenteropathy, and necrotising enterocolitis.

• Small amounts of blood and mucus mixed with, or streaking, otherwise normal stools, sometimes loose stools; mild fussiness, flatulence, or increased stool frequency; the baby feeds well and has normal weight gain; no vomiting, fever, abdominal distension or systemic illness.
• Examination: well looking infant, normal growth, soft abdomen, perianal inspection (fissure, dermatitis), stool testing.
• Red flags (consider other diagnoses): faltering growth; anaemia or pallor; severe diarrhoea or dehydration; persistent vomiting; abdominal distension; bilious vomiting; fever; lethargy; large volume bloody stools (intussusception, necrotising enterocolitis, infectious colitis, coagulopathy, vitamin K deficiency bleeding); onset after 6 months; red currant jelly stool; paroxysmal drawing up of legs.

• Clinical diagnosis: typical age, well infant with visible blood in stool, and response to elimination.
• Stool occult blood and microscopy (eosinophils) may support; stool culture if diarrhoea or fever.
• Exclude anal fissure by inspection, infection, intussusception, malrotation, necrotising enterocolitis, Hirschsprung enterocolitis and coagulopathy (vitamin K deficiency).
• Full blood count and ferritin if prolonged bleeding or pallor; coagulation screen if bruising or other bleeding.
• Diagnostic elimination: 2 to 4 weeks of cow's milk protein exclusion; bleeding usually resolves in 72 to 96 hours but may take 2 to 4 weeks; reintroduction (challenge) at 9 to 12 months confirms but is optional if the infant is thriving.
• Allergy tests (skin prick, specific IgE) are negative in non-IgE disease and are not indicated.
• Endoscopy is rarely needed (reserved for persistent bleeding despite elimination, anaemia or faltering growth).

• Reassure parents that it is a benign, transient condition.
• Breastfed infants: continue breastfeeding; the mother excludes cow's milk protein (and, if there is no response within 2 to 4 weeks, also soy and egg) from her diet; maternal calcium 1000 mg daily and vitamin D 10 micrograms (400 IU) daily; maintain supervision by a dietitian. Reintroduce dairy to the mother's diet only after the infant has reached 9 to 12 months or when blood has cleared and by dietitian plan.
• Formula fed infants: extensively hydrolysed formula (eHF); amino acid formula for those who fail to respond within 2 to 4 weeks; soy formula is not preferred (cross reactivity).
• Continue the elimination until 9 to 12 months of age (or 6 months after symptom resolution), then reintroduce cow's milk protein stepwise at home under dietitian guidance (milk ladder), or by supervised challenge if prior severe symptoms.
• Treat any iron deficiency: ferrous sulfate 3 to 6 mg elemental iron/kg/day orally for 3 months.
• Do not use acid suppression or steroids.
• Follow up at 2 to 4 weeks (response), then every 3 months for growth; refer for failure to respond, faltering growth, anaemia, or severe symptoms.